Brake With a Reed Switch for Indicating an Operating Condition of the Brake

Abstract

A brake is provided that employs an electromagnetic or magnetic circuit to disengage the brake and in which a reed switch is used to indicate an operating condition of the brake. The reed switch is positioned across an air gap between two members of the electromagnetic or magnetic circuit. The state of the reed switch changes in response to flux leakage at the air gap and may be used to monitor for potential failures in the operation of the brake including a failure to operate due a lack of current or the failure of the brake to disengage due to an obstruction.

What is claimed is: 
     
         1 . A brake, comprising:
 a friction plate configured for coupling to a shaft for rotation with the shaft about an axis of rotation;   a pressure plate disposed about the axis on a first side of the friction plate and fixed against rotation;   an armature plate disposed about the axis on a second side of the friction plate;   a field shell disposed about the axis on an opposite side of the armature plate relative to the friction plate;   a spring biasing the armature plate in a first axial direction towards the friction plate and away from the field shell to engage the brake;   a conductor disposed within the field shell, current supplied to the conductor creating an electromagnetic circuit including the armature plate and the field shell, the electromagnetic circuit urging the armature plate in a second axial direction away from the friction plate and towards the field shell to disengage the brake; and,   a first reed switch extending across an air gap between first and second members of the electromagnetic circuit, a state of the first reed switch indicative of an operating condition of the brake.   
     
     
         2 . The brake of  claim 1  wherein a longitudinal axis of the first reed switch extends in a direction other than parallel to the axis of rotation. 
     
     
         3 . The brake of  claim 1  wherein the first and second members of the electromagnetic circuit comprise the armature plate and the field shell. 
     
     
         4 . The brake of  claim 3  wherein the reed switch is disposed radially outwardly of the armature plate and the field shell. 
     
     
         5 . The brake of  claim 1  wherein the longitudinal axis of the first reed switch extends in a direction other than parallel to a direction of a magnetic force at a point in the air gap where the magnetic force is greatest. 
     
     
         6 . The brake of  claim 1  wherein the first reed switch is adjacent to the air gap and configured to detect flux leakage at the air gap when the armature plate is spaced from the field shell. 
     
     
         7 . A brake, comprising:
 a friction plate configured for coupling to a shaft for rotation with the shaft about an axis of rotation;   a pressure plate disposed about the axis on a first side of the friction plate and fixed against rotation;   an armature plate disposed about the axis on a second side of the friction plate;   a field shell disposed about the axis on an opposite side of the armature plate relative to the friction plate;   a spring biasing the armature plate in a first axial direction towards the friction plate and away from the field shell to engage the brake;   a conductor disposed within the field shell, current supplied to the conductor creating an electromagnetic circuit including the armature plate and the field shell, the electromagnetic circuit urging the armature plate in a second axial direction away from the friction plate and towards the field shell to disengage the brake; and,   a first reed switch extending across an air gap between first and second members of the electromagnetic circuit, a state of the first reed switch indicative of an operating condition of the brake   wherein, during proper operation of the brake, the first reed switch undergoes a first transition from a first state to a second state when the brake is engaged and current begins flowing through the conductor and subsequently undergoes a second transition from the second state back to the first state once the brake is disengaged.   
     
     
         8 . The brake of  claim 7 , further comprising a controller coupled to the first reed switch and configured to generate a signal indicative of a lack of current in the conductor when the first reed switch fails to undergo the first transition. 
     
     
         9 . The brake of  claim 8 , wherein the controller is configured to generate a signal indicative of a failure to disengage by the brake when the first reed switch fails to undergo the second transition. 
     
     
         10 . The brake of  claim 7 , further comprising a controller configured to generate a signal indicative of a failure to disengage by the brake when the first reed switch fails to undergo the second transition. 
     
     
         11 . The brake of  claim 7 , further comprising a second reed switch extending across the air gap between the first and second members of the electromagnetic circuit, the second reed switch circumferentially spaced from the first reed switch and a state of the second reed switch indicative of an operating condition of the brake. 
     
     
         12 . The brake of  claim 7  wherein a longitudinal axis of the first reed switch extends in a direction other than parallel to the axis of rotation. 
     
     
         13 . A brake, comprising:
 a friction plate configured for coupling to a shaft for rotation with the shaft about an axis of rotation;   a pressure plate disposed about the axis on a first side of the friction plate and fixed against rotation;   an armature plate disposed about the axis on a second side of the friction plate;   a field shell disposed about the axis on an opposite side of the armature plate relative to the friction plate, the field shell including first and second components;   a spring biasing the armature plate in a first axial direction towards the friction plate and away from the field shell to engage the brake;   a permanent magnet disposed between the first and second components of the field shell and forming a magnetic circuit with the first and second components of the field shell and the armature plate, the magnetic circuit urging the armature plate in a second axial direction away from the friction plate and towards the field shell to disengage the brake; and,   a first reed switch extending across an air gap between first and second members of the magnetic circuit, a state of the first reed switch indicative of an operating condition of the brake.   
     
     
         14 . The brake of  claim 13  wherein a longitudinal axis of the first reed switch extends in a direction other than parallel to the axis of rotation. 
     
     
         15 . The brake of  claim 14  wherein the longitudinal axis of the first reed switch extends in a direction other than parallel to a direction of a magnetic force at a point in the air gap where the magnetic force is greatest. 
     
     
         16 . The brake of  claim 13  wherein the first and second members comprise the first and second components of the field shell. 
     
     
         17 . The brake of  claim 16  wherein the first reed switch is disposed radially outwardly of the first and second components of the field shell. 
     
     
         18 . The brake of  claim 13  wherein the first reed switch is adjacent to the air gap and configured to detect flux leakage at the air gap when the armature plate is spaced from the field shell. 
     
     
         19 . The brake of  claim 13  further comprising a conductor disposed within the field shell, current of a first polarity supplied to the conductor increasing a force of the magnetic circuit and current of a second polarity supplied to the conductor weakening the force of the magnetic circuit. 
     
     
         20 . The brake of  claim 13 , further comprising a second reed switch extending across the air gap between the first and second members of the electromagnetic circuit, the second reed switch circumferentially spaced from the first reed switch and a state of the second reed switch indicative of an operating condition of the brake.